Introduction
Due to increase in population construction of high rise buildings has
become very common. However, 8 to 10 storyed residential apartment
constructions are very common, as such buildings have a total height less
than 30 metres and column-beam structure is sufficient to resist wind

pressures and special provision of shear wall or other is not required.
The cost of foundation, however, is always large due to construction
of Raft Foundation in general. It is not essential to provide raft, but
Indore being a belt of Black Cotton Soil, it is preferable to construct
raft. In this paper, we have compared Raft Foundation with that of
Strap Beam Foundation and have shown that Strap Beam Foundation is
economical than that of Raft. We have also provided Strap foundation in
one building and saved cement as well as reinforcing bars considerably
thereby reducing construction cost considerably.

Case Study
The building under consideration is a G+8 storyed apartment
building under construction at Pagnis Nagar, Indore. The plot size is
16,000 Sq.ft. with ground coverage of 30% i.e. 4800 Sq.ft. The total

Dr. S. V. Deodhar
Consultant, Indore

constructed area of all the floors is 43,200 Sq.ft. Four floors of this
building are completed, and rest is in progress. The building foundation
was designed for Raft as well as for Strap Beam foundation. The building
was designed using STAAD PRO software and then checked as per Codal
provisions. The typical floor plan of ground floor and other floors are
shown in Figure 1 and foundation plan using Raft foundation and Strap
Beam foundation is shown in Figure 2.Design Considerations
The design considerations are as given below. The total height of
building above ground level is 26.15m. The structure was designed
using STAAD-PRO Software.Loading
Wall load: 200 mm wall = 12.54 kN/m; 100 mm Wall = 6.27 kN/m;
100mm Parapet wall = 2.85 kN/m
Slab Load: Dead Load = 6.53 kN/m2; Live Load = 2.5 kN/m2
Wind load: As per IS 875

Assumed Stresses
Compressive Stress in Concrete Fck = 20 N/mm2
Yield Tensile Stress in Steel FY = 415 N/mm2
Ultimate bearing capacity of soil Q (Ultimate) = 225 kN/m2
Safe bearing capacity of soil Q (Safe) = 120 kN/m2
Concrete Mix = M 20 Grade
Comparison
In comparison, the quantity of material required for the design of
“Raft Foundation” and “Strap Beam Foundation” is shown in Table. It
shows the quantities of Steel and Cement saved by using Strap Beam
Foundation with that to Raft Foundation.
Conclusion
It is found that in actual practice the conventional foundation
(raft) consumed more steel as well as concrete as compared with the
strap beam foundation (costonomical foundation). Hence it is proved
that providing costonomical strap beam foundation is economical
to make the structure economical and financially sustainable. This
makes the structure cheaper. keeping the other considerations like
Safety, Security and User friendliness. It is therefore recommended
that for medium rise buildings Strap foundation be used in place of
Raft foundation.

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